Self-destructing apparatus for impact-detonating explosive devices

ABSTRACT

A self-destructing apparatus for impact-detonating explosive devices having a piezoelectric fuze responsive to sonic waves for detonation of the device. The apparatus includes means responsive to at least one of firing or dropping of the impact-detonating explosive device for triggering a sonic wave generator after a predetermined time delay, the sonic wave produced by the generator being transmitted to the piezoelectric fuze for detonation of the explosive device, thereby ensuring destruction of the device.

United States-Patent [191 Rob et a1.

[ June 11, 1974' SELF-DESTRUCTING APPARATUS FOR IMPACT-DETONATINGEXPLOSIVE DEVICES [75] Inventors: Peter Roh; Manfred Strunk, both ofTroisdorf, Germany [73] Assignee: Dynamit Nobel Aktiengesellschaft,

Troisdorf, Germany 22 Filedz Nov.28, 1972 21 Appl. No.: 310,092

[52] US. Cl. 102/70.2 GA, 102/74, 102/78, 102/83 [51] Int. Cl...... F42c1l/02, F22c 9/00, F426 11/06 [58] Field of Search.. 102/70.2 GA, 70.2 R,70.2 A, 102/72, 71, 74,78, 82, 83, 84, 85, 85.6

[56] References Cited UNITED STATES PATENTS 2,515,040 7/1950 Hatcher102/72 2,827,851 3/1958 Ferrara 102/70.2 GA 2,870,712 l/1959 Brown et a1l02/70.2 GA

2,938,461 Rabinow 102/70.2 R 3,043,222 7/1962 Kaspanl l02/70.2 R3,078,802 2/1963 Sturrock 102/72 3,320,890 5/1967 Ciccone et a1...l02/70.2 GA 3,356,026 12/1967 Lubig 102/702 GA 3,371,608 3/1968 Webb102/72 Primary Examiner-Samuel W. Engle Assistant ExaminerC. T. JordanAttorney, Agent, 0r Firm-Craig & Antonelli [5 7] 'ABSTRACT Aself-destructing apparatus for impact-detonating explosive deviceshaving a piezoelectric fuze responsive to sonicwaves for detonation ofthe device. The apparatus includes means responsive to at least one offiring or dropping of the impact-detonating explosive device fortriggering a sonic wave generator after a predetermined time delay, thesonic wave produced by the generator being transmitted to thepiezoelectric fuze for detonation of the explosive device, therebyensuringdestruction of the device.

14 Claims, 3 Drawing Figures AWQM L j PATENTEDJUM 1 1 m4 3.815.505

HGI

FIG

SELF-DESTRUCTING APPARATUS'FOR IMPACT-DETONATING EXPLOSIVE DEVICES Thepresent invention relates to a self-destruction device for explosivedevices detonating'on impact, such as, for example, projectiles,rockets, or bombs, having a piezoelectric fuze which can be triggered bysonic shock waves.

Many varieties of piezoelectric detonators are known for projectiles,rockets, bombs, or the like, and described in detail, for example, inUS. Pat. No. 3,356,026. It is furthermore known from US. Pat. No.2,894,457 thatpiezoelectricfuzescanbe triggered by sonic shock waveswhich are produced in the explosive device when impinging upon thetarget after having been fired or dropped with the sonic waves passingvia the .wall of the explosive device to the detonator for generatingthe ignition voltage in the piezo crystal.

For reasons of safety, it is basically desirable to construct percussiveexplosive devices, if at all possible, in such a manner that theyself-destruct, if they fail to detonate by contact with the targetwithin a predetermined period of time after firing or dropping.

Accordingly, it'is. the objective of the present invention to provide animpact explosive device with a piezoelectric fuzev'vhich can betriggered by sonic waves and to artificially produce in the percussionexplosive device, a sonic wave for triggering the piezoelectric fuzeafter the elapse of a predetermined time interval after firing ordropping of the explosive device.

stant of ignition of the detonator, so that the sonic wave,

produced during the reaction of the detonator is transmitted to thepiezoelectric fuze. The manner in which the spatial arrangement of thepiezoelectric fuze and the detonator is advantageously provided, i.e.,whether these components are disposed, for example, separately from eachother or in a parallel or series disposition in a common housing,depends on the requirements in each individualcase. However, in anyevent, the important factor is a maximally advantageous soundtransmission from thedetonator to the piezo crystal, so that a detonatorof such .a size'is utilized which cannot ignite or damage the impactexplosive device directly, i.e., circumventing the piezoelectric fuze.Such an arrangement thus ensures that it is impossible for the impactexplosive device to become inoperable or even to detonate in case of anunintended premature triggering of the self-destruction device i.e., aslong as the piezoelectric fuze is still in the safety position.

The delay line can be constructed conventionally on an electronic basis,by providing that electrical energy, supplied upon the firing ordropping of the percussion explosive device, for example, from theoutside, is transmitted via capacitors, resistors and other circuitcomponents with a desired delay to an electrically ignitable detonator.However, in order to be able to construct the fuze with theself-destruction unit advantageously as a self-contained, compactstructural device without extraneous electrical contacts, in accordancewith the present invention, the delay line may be selected in a knownmanner as a pyrotechnical mixture ignitable with the aid of an impactorfriction-sensitive primer element and to maintain, at a spacing from theprimer element, an ignition pin in a locked position which can beovercome, likewise in a conventional manner, by inertial forces,this-pin being movable toward the primer element by means of inertialforces, spring force, or the like. In this connection, it is, of course,also within the teachings of the present invention to employ, in placeof the hitting or striking primer element with firing pin or strikerpin, an electrically ignitable primer element which derives theelectrical energy required for ignition, for example, from a batteryinstalled therein.

In accordance with another embodiment of the present invention, thedelay process, as well as the sound generation, are effectedmechanically by holding a striker pin at a spacing from an impingementsurface associated with the piezoelectric fuze by means of a lockingaction, against the force of a compression spring, which locking actioncan be overcome in a conventional manner by inertial forces. The strikerpin is provided with a serration, anda conventional blocking gear meshestherewith, so that the movement of the fir ing pin against theimpingement surface can be retarded in a predetermined manner. Thestriking surface is in such a spatial arrangement with respect to thefuze that the satisfactory sound transmission'to the piezo crystal isalso ensured in this case. I

A particularly favorable transmission of the sonic waveto the piezocrystal is obtained by providing that theimpingement surface is part ofone of the two abutments of the piezoelectric fuze. The abutmentcontacting the piezo crystal is constructed so that it can absorb theimpact forces occurring upon impingment of the striker pin, without thefunction of the piezoelectric fuze being impaired thereby.

In case a reinforcement of the impact power of the striker piniisconsidered advantageous, inaccordance with a further feature of thepresent invention, the impingement surface is formed as part of animpactsensitive detonator, from which the sonic wave is then transmittedto the piezo crystal.

These and further objects, features and advantages of thepresent-invention will become more obvious from the followingdescription when taken in connection with the accompanying drawingswhich show, for purposes of illustration only, several embodiments inaccordance with the present invention, and wherein FIG. 1 is alongitudinal sectional view of a piezoelectric fuze with aself-destructing device provided with a pyrotechnical delay unit;

FIG. 2 is a longitudinal sectional view of a piezoelectric fuze with aself-destructing device provided with a mechanical delay unit; and

FIG. 3 is a schematic circuit diagram for an electronicdelay unit inaccordance with the present invention.

Referring now to the drawings wherein like reference numerals areutilized to designate like parts throughout the several views and moreparticularly to FIG. I, a piezoelectric fuze and a self-destructingdevice are disposed side-by-side in an outer housing 23, which can beinserted, for example, in the bottom of a projectile, not shown, with apropagation charge 9 arranged at one end pointing into the flightdirection. The piezoelectric fuze is installed in the housing 1 and isprovided with a safety mechanism for placing the fuze in the armedcondition only during or shortly after the firing of the projectile. Forthis purpose, a spring 2 is compressed by a stud 3 upon firing, by theinertia of the latter, so that an arming ball 4 is released and a rotor5 can be pivoted by a biased torsion spring 6, to such an extent that adetonator 7 contacts with its central contact, not shown, a displaceablyarranged contact element 8 and comes into engagement with thepropagation charge 9 with its opposed end face for placing the fuze inthe armed position. The contact element 8 is in electrically conductiveconnection via a compression spring 10 and one abutment 24 with a piezocrystal 11, which crystal is insulated on one side from the housing 1 bymeans of an insulating cup 12. The other side of the piezo crystal 11 isin electrically conductive connection with the outer casing of theelectrically ignitable detonator 7 via another abutment 13, the housing1, and the rotor 5. Upon the impingement of a sonic wave on the fuze, anelectric voltage is produced in the piezo crystal 11 which serves forigniting the detonator 7.

An annular casing 14 is disposed around the housing I and theself-destructing device is arranged within two parallel-arranged boresof the casing. Upon firing, a pin 16 is displaced, due to its inertia,toward the rear against the bias of spring such that an arming ball 17is released. The arming ball 17 serves for locking a primer pin 18 in aninitial position such that upon release of the ball 17, the primer pin18 which is constructed as a striker pin moves from its locked positiondue to its inertia, toward the rear and against a frictionsensitiveprimer element 19, whereby the latter is ignited. This primer element19, in turn, ignites a pyrotechnical mixture provided thereafter, which,after burning through within a predetermined delay period, ignites aflash-sensitive detonator 21. The detonator 21, during its reaction,produces a sonic wave traveling, via the metallic components which arein contact with one another with a minimum amount of play, to the piezocrystal 11, generating at that point the electrical voltage required forigniting the detonator 7.

Conventional mixture compositions can be employed for the primer element19, the delay line with the pyrotechnical mixture 20, and for thedetonator 21, which are advantageously combined into a unit within acommon casing 25. For example, a mixture of tetrazene andtrinitroresorcinate can be used for the friction-sensitive primerelement 19; a mixture of antimony, potassium chlorate, and lead chromatecan be employed for the pyrotechnical mixture 20; and twoseries-connected compressed components of lead azide and penthrite canbe utilized for the detonator 21, wherein the compressed unit of theflame-sensitive lead azide is disposed adjacent to the pyrotechnicalmixture 20. The strength of the detonator 21 is dimensioned so that itproduces, on the one hand, a sonic wave sufficient for triggering thepiezoelectric fuze, but, on the other hand, is incapable of detonatingthe projectile directly, or even to cause damage to the projectile.

The embodiment illustrated in FIG. 2 corresponds to that of FIG. 1 withrespect to the piezoelectric fuze, so that the same components have beenprovided with identical reference numerals. In this embodiment, theself-destructing device is constructed as a purely mechanical device andis disposed behind the piezoelectric fuze. However, it is also possibleto arrange this self-destructing device beside the fuze, if this shouldits locked position. The thus-released striker pin 27 is set intomotionby means of a pretensioned compression spring 26. The striker pin 27 haslateral extending teeth or serrations 31, meshing with a gear wheel '28which, due to the gear inhibitor 29, can rotate only in an inhibitedmanner. The construction of the gear inhibitor 29 is known, inprinciple, from German Offen- Iegungsschrift 1,927,911. As shown, theteeth 31 do not extend to the rear end of the striker pin 27, so that.the latter is accelerated without impediment by means of thecompression spring 26 in the end portion of its forward movement. Thestriker pin impinges on the impact surface 32 of the abutment 13 of thepiezoelectric fuze and thereby produces a sonic wave resulting in theresponse of the fuze. In front of the abutment 13, apercussion-sensitive detonator, not shown, may be arranged in oppositionto the striker pin 27 in order to produce a stronger sonic wave. Theabutment l3 rests on the housing 22 with the interposition of anelastic, electrically conductive member, e.g., one or several cupsprings 33, to ensure that the abutment is in sufficient intimatecontact with the piezo crystal 11.

In accordance with another embodiment of the present invention, anelectronic delay line is illustrated in FIG. 3, wherein a capacitor C ischarged in a conventional manner via two electrodes E and E Theelectrodes E, and E are disposed on the outer surface of the jacket ofthe impact explosive device in such a manner that, during the firingand/or dropping of the impact explosive device from a barrel or, forexample, a bomb well, they are in contact for a sufficient length oftime with energized counter electrodes disposed at that point. Acapacitor C is charged in a predetermined manner via the resistor R bythe capacitor C for such a period of time until the flashover voltage ofa spark gap device F has been reached. Thereafter, the capacitor C isdischarged via the spark gap device F and an electrically ignitabledetonator D, which detonator produces the sonic wave required fortriggering .the piezoelectric fuze arranged proximate thereto as in theFIG. 1 and FIG. 2 embodiments.

Obviously, many modifications and variations of the present inventionare possible in the light of the above teachings. It should therefore beunderstood that within the scope of the appended claims, the inventionmay be sive device for triggering said sonicwave generating means aftera predetermined period of delay to generate sonic waves for triggeringof the piezoelectric fuze to effect detonation" of the explosive,whereby the selfdestructing apparatus is only indirectly effective onthe.

explosive via the piezoelectricfuze of the impact detonating device.

2. Self-destructing apparatus according to claim 1, wherein said sonicgenerating means includes a detonatorand' said means for triggering saidsonic wave generating means includes delay means for igniting saiddetonator after the predetermined period of delay, the sonic wavegenerated during the reaction of said detonator being transmitted to thepiezoelectric fuze.

3. Self-destructing apparatus according to claim 2, wherein said delaymeans includes a pyrotechnical mixture having a predetermined burningtime, said mixture being ignitable by primer element means, said meansfor triggering said sonic wave generating means further includingmovable primer pin means, locking means for retaining the primer pinmeans in a first position, said locking means being responsive to atleast one of firing and. dropping of the impact-detonating explosive-device for releasing said primer pin means to permit the movementthereof, said primer pin means being movable from the first positionwhich is spaced from said primer element means to contact said primerelement means for igniting the pyrotechnical mixture.

4. Self-destructing apparatus according to claim 3, wherein said primerelement means is one of an impact sensitive and friction sensitiveprimer element.

5. Self-destructing apparatus according to claim 3, wherein said lockingmeans is responsive to inertial forces upon at least one of firing anddropping the impact-detonating explosive device for releasing saidprimer pin means.

6. Self-destructing apparatus according to claim 3, wherein said primerpin means is movable from the first position to contact the primerelement means by inertial forces.

7. Self-destructing apparatus according to claim 3, wherein said primerpin means includes a primer pin and spring means biasing said primer pintoward said primer element means, said spring means moving said pin intocontact with said primer element means upon release of said primer pin.

8. Self-destructing apparatus according to claim 1, wherein said sonicwave generating means includes striker pin means biased for movementagainst an impingement surface proximate to the piezoelectric fuze forproducing the sonic waves, and said triggering means for said sonic wavegenerating means includes locking means for retaining said striker pinmeans in a first position spaced from the impringement surface andresponsive to at least one of firing and dropping the impact-detonatingexplosion device for releasing said striker pin means for movementtoward the impingement surface, and delay means for controlling thespeed of movement of the striker pin during at least a portion of thepath of movement between the first position and the impingement surface.

9. Self-destructing apparatus according to claim 8, wherein the delaymeans is an inhibiting gear meshing with serrations provided on saidstriker pin means along at least a portion of the surface thereof.

10. Self-destructing apparatus according to claim 8, wherein said sonicwavegenerating means includes a striker pin and a compression spring forbiasing said striker pin in the direction toward the impingementsurface.

ll. Self-destructing apparatus according to claim 8, whereinsaidimpingement surface is an abutment surface of the piezoelectricfuze.

12. Self-destructing apparatus according to claim 8, wherein saidimpingement surface is a part of a percussion-sensitive detonator.

l3. Self-destructing apparatus according to claim 1, wherein said meansfor triggering said sonic wave gen erating means is electronic circuitmeans responsive to at least one of firing and dropping oftheimpactdetonating explosive device for providing an electrical triggeringsignal and said sonic wave generating means is an electrically ignitabledetonator responsive to the electrical triggering signal.

14. Self-destructing apparatus according to claim 13, wherein theelectronic circuit means includes first and second electrodes energizedduring at least one of the firing and dropping of the impact-detonatingexplosive device, a first capacitor having first and second terminalsconnected respectively to said first and second electrodes, a resistorhaving one terminal connected to the first terminal of said firstcapacitor, a second capacitor having a first terminal connected to theother terminal of said resistor and a second terminal connected to thesecond terminal of the first capacitor, a spark gap device having oneterminal connected to the other terminal of said resistor and anotherterminal connected to one terminal of said electrically ignitabledetonator, said detonator having another terminal connected to thesecond terminal of the second capacitor.

1. Self-destructing apparatus for impact-detonating explosive deviceshave a piezoelectric fuze responsive to sonic waves generated uponimpact of the explosive device for the detonation of an explosive of theexplosive device, the self-destructing apparatus comprising sonic wavegenerating means for generating sonic waves to trigger the piezoelectricfuze of the impactdetonating device, and means responsive to at leastone of firing and dropping of the impact-detonating explosive device fortriggering said sonic wave generating means after a predetermined periodof delay to generate sonic waves for triggering of the piezoelectricfuze to effect detonation of the explosive, whereby the self-destructingapparatus is only indirectly effective on the explosive via thepiezoelectric fuze of the impact detonating device.
 2. Self-destructingapparatus according to claim 1, wherein said sonic generating meansincludes a detonator and said means for triggering said sonic wavegenerating means includes delay means for igniting said detonator afterthe predetermined period oF delay, the sonic wave generated during thereaction of said detonator being transmitted to the piezoelectric fuze.3. Self-destructing apparatus according to claim 2, wherein said delaymeans includes a pyrotechnical mixture having a predetermined burningtime, said mixture being ignitable by primer element means, said meansfor triggering said sonic wave generating means further includingmovable primer pin means, locking means for retaining the primer pinmeans in a first position, said locking means being responsive to atleast one of firing and dropping of the impact-detonating explosivedevice for releasing said primer pin means to permit the movementthereof, said primer pin means being movable from the first positionwhich is spaced from said primer element means to contact said primerelement means for igniting the pyrotechnical mixture. 4.Self-destructing apparatus according to claim 3, wherein said primerelement means is one of an impact sensitive and friction sensitiveprimer element.
 5. Self-destructing apparatus according to claim 3,wherein said locking means is responsive to inertial forces upon atleast one of firing and dropping the impact-detonating explosive devicefor releasing said primer pin means.
 6. Self-destructing apparatusaccording to claim 3, wherein said primer pin means is movable from thefirst position to contact the primer element means by inertial forces.7. Self-destructing apparatus according to claim 3, wherein said primerpin means includes a primer pin and spring means biasing said primer pintoward said primer element means, said spring means moving said pin intocontact with said primer element means upon release of said primer pin.8. Self-destructing apparatus according to claim 1, wherein said sonicwave generating means includes striker pin means biased for movementagainst an impingement surface proximate to the piezoelectric fuze forproducing the sonic waves, and said triggering means for said sonic wavegenerating means includes locking means for retaining said striker pinmeans in a first position spaced from the impringement surface andresponsive to at least one of firing and dropping the impact-detonatingexplosion device for releasing said striker pin means for movementtoward the impingement surface, and delay means for controlling thespeed of movement of the striker pin during at least a portion of thepath of movement between the first position and the impingement surface.9. Self-destructing apparatus according to claim 8, wherein the delaymeans is an inhibiting gear meshing with serrations provided on saidstriker pin means along at least a portion of the surface thereof. 10.Self-destructing apparatus according to claim 8, wherein said sonic wavegenerating means includes a striker pin and a compression spring forbiasing said striker pin in the direction toward the impingementsurface.
 11. Self-destructing apparatus according to claim 8, whereinsaid impingement surface is an abutment surface of the piezoelectricfuze.
 12. Self-destructing apparatus according to claim 8, wherein saidimpingement surface is a part of a percussion-sensitive detonator. 13.Self-destructing apparatus according to claim 1, wherein said means fortriggering said sonic wave generating means is electronic circuit meansresponsive to at least one of firing and dropping of theimpact-detonating explosive device for providing an electricaltriggering signal and said sonic wave generating means is anelectrically ignitable detonator responsive to the electrical triggeringsignal.
 14. Self-destructing apparatus according to claim 13, whereinthe electronic circuit means includes first and second electrodesenergized during at least one of the firing and dropping of theimpact-detonating explosive device, a first capacitor having first andsecond terminals connected respectively to said first and secondelectrodes, a resistor having one terminal connected to the firstterminal of said first capacitor, a second capacitor having a firstterminal connected to the other terminal of said resistor and a secondterminal connected to the second terminal of the first capacitor, aspark gap device having one terminal connected to the other terminal ofsaid resistor and another terminal connected to one terminal of saidelectrically ignitable detonator, said detonator having another terminalconnected to the second terminal of the second capacitor.